This invention relates to switches, and in the preferred embodiment provides two improved switches of the type having an elastomeric body which cooperates with components mounted on a printed circuit board (PCB) to provide a switch.
Switches of the general type comprising an elastomeric body and a printed circuit board which cooperate to form a switch are well known and are frequently used for controlling electrical connections in relatively hostile environments, for example in wet conditions, or areas of high humidity, or in relatively dirty environments such as certain industrial sites. The switches proposed heretofore all suffer from certain disadvantages, and in particular are either complex and time consuming to assemble or mount or provide inadequate sealing of the electric contacts against the ingress of moisture and dirt from the surrounding environment.
The preferred switches of the present invention offer improved sealing against the ingress of moisture or dirt into the area of the electrical contacts and interior of the equipment from the mounting hole for the switch, and offer a number of other advantages as compared with the prior art.
According to a first aspect of the present invention a switch comprises an elastomeric body shaped to define a recess for receiving a printed circuit board (PCB); a PCB mounted to the body in the recess to define with the body a closed switch cavity; fixed electrical contacts provided on the PCB within the switch cavity, and at least one movable contact provided in the switch cavity, a portion of the body being resiliently deformable to bring the movable contact into engagement with the fixed contacts to establish an electrical connection therebetween.
The fact the PCB is mounted to the body to define therewith a closed switch cavity substantially simplifies construction of the switch and provides a means for excluding moisture and dirt from the area of the electrical contacts.
In preferred embodiments of the invention the body recess defines a groove in which the periphery of the PCB is mounted to provide the required closing of the switch cavity. If desired, the interface between the groove and the PCB may be sealed with an appropriate sealant. If desired the layer of sealant may be provided in the body recess on the side of the PCB remote from the switch cavity to ensure a hermetic seal between the PCB and the body.
The fixed contacts may be electrically connected to flex tails to provide electrical connections to the contacts. In the alternative, the contacts may be connected to pins or a socket mounted on the PCB to cooperate respectively with a socket, wires or the pins of a connector device.
In one embodiment of the invention the movable contact is mounted on the deformable portion of the body. In alternative embodiments a contact disc may be provided within the switch cavity to be acted upon by the deformable portion of the body. The disc may be configured to provide normally open, normally closed, or momentary make connections between the fixed contacts.
If desired, the body may be formed of a transparent or translucent material and one or more indicator or illumination devices may be provided on the PCB in the switch cavity to provide illumination to the switch and/or contact status information.
The preferred embodiments of the invention may be mounted on a panel from the front thereof with little or no access being required to the switch from the rear of the panel to effect. Typically, switches may be secured to the panel either using an elastomeric deformable skirt on the body or using mounting clips provided for the purpose on the body or on the PCB.
By appropriate choice of material for the body the switch cannot only be made robust and relatively inexpensive, but it can also readily be customised to the particular application for which it is intended. In particular, custom legends may be printed directly onto the body and/or a metal key faceplate may be secured to the body.
Depending upon the particular applications for which the switch is intended the PCB may be a conventional rigid PCB or may be a flex circuit or ITO.
In one preferred embodiment of the invention the switch is configured as a single push momentary action switch. In an alternative embodiment of the invention the switch is embodied as a rocker switch. The rocker switch may include contacts under only one end portion of the switch (thereby simulating a simple on-off rocker switch), or may incorporate contacts under two spaced apart end portions of the switch (thereby simulating a changeover switch), or may incorporate contacts under two end portions of the switch and under a centre portion to provide a range of relatively complex switch simulations.